v0.4.3 (2023-09-13)

v0.4.2 (2023-09-04)

  • put_plug: Handle response streaming on Plug 1.15+.

  • Don't warn on mixed-case header names

v0.4.1 (2023-09-01)

  • Fix Req.Request Inspect regression

v0.4.0 (2023-09-01)

Req v0.4.0 changes headers to be maps, adds request & response streaming, and improves steps.

Change Headers to be Maps

Previously headers were lists of name/value tuples, e.g.:

[{"content-type", "text/html"}]

This is a standard across the ecosystem (with minor difference that some Erlang libraries use charlists instead of binaries.)

There are some problems with this particular choice though:

  • We cannot use headers[name]
  • We cannot use pattern matching

In short, this representation isn't very ergonomic to use.

Now headers are maps of string names and lists of values, e.g.:

%{"content-type" => ["text/html"]}

This allows headers[name] usage:

#=> ["text/html"]

and pattern matching:

case Req.request!(req) do
  %{headers: %{"content-type" => ["application/json" <> _]}} ->
    # handle JSON response

This is a major breaking change. If you cannot easily update your app or your dependencies, do:

# config/config.exs
config :req, legacy_headers_as_lists: true

This legacy fallback will be removed on Req 1.0.

There are two other changes to headers in this release.

Header names are now case-insensitive in functions like Req.Response.get_header/2.

Trailer headers, or more precisely trailer fields or simply trailers, are now stored in a separate trailers field on the %Req.Response{} struct as long as you use Finch 0.17+.

Add Request Body Streaming

Req v0.4 adds official support for request body streaming by setting the request body to an enumerable. Here's an example:

iex> stream = Stream.duplicate("foo", 3)
iex>!("", body: stream).body["data"]

The enumerable is passed through request steps and they may change it. For example, the compress_body step gzips the request body on the fly.

Add Response Body Streaming

Req v0.4 also adds response body streaming, via the :into option.

Here's an example where we download the first 20kb (by making a range request, via the put_range step) of Elixir release zip. We stream the response body into a function and can handle each body chunk. The function receives a {:data, data}, {req, resp} and returns a {:cont | :halt, {req, resp}} tuple.

resp =
    url: "",
    range: 0..20_000,
    into: fn {:data, data}, {req, resp} ->
      IO.inspect(byte_size(data), label: :chunk)
      {:cont, {req, resp}}

# output: 17:07:38.131 [debug] redirecting to
# output: chunk: 16384
# output: chunk: 3617

resp.status #=> 206
resp.headers["content-range"] #=> ["bytes 0-20000/6801977"]
resp.body #=> ""

Notice we only stream response body, that is, Req automatically handles HTTP response status and headers. Once the stream is done, Req passes the response through response steps which allows following redirects, retrying on errors, etc. Response body is set to empty string "" which is then ignored by decompress_body, decode_body, and similar steps. If you need to decompress or decode incoming chunks, you need to do that in your custom into: fun function.

As the name :into implies, we can also stream response body into any Collectable. Here's a similar snippet to above where we stream to a file:

resp =
    url: "",
    range: 0..20_000,

# output: 17:07:38.131 [debug] redirecting to (...)
resp.status #=> 206
resp.headers["content-range"] #=> ["bytes 0-20000/6801977"]
resp.body #=> %File.Stream{}


  • Change request.headers and response.headers to be maps.

  • Ensure request.headers and response.headers are downcased.

    Per RFC 9110: HTTP Semantics, HTTP headers should be case-insensitive. However, per RFC 9113: HTTP/2 headers must be sent downcased.

    Req headers are now stored internally downcased and all accessor functions like Req.Response.get_header/2 are downcasing the given header name.

  • Add trailers field to Req.Response struct. Trailer field is only filled in on Finch 0.17+.

  • Make request.registered_options internal representation private.

  • Make request.options internal representation private.

    Currently request.options field is a map but it may change in the future. One possible future change is using keywords lists internally which would allow, for example, [a: 1]) |> Req.update(params: [b: 2]) to keep duplicate :params in request.options which would then allow to decide the duplicate key semantics on a per-step basis. And so, for example, put_params would merge params but most steps would simply use the first value.

    To have some room for manoeuvre in the future we should stop pattern matching on request.options. Calling request.options[key], put_in(request.options[key], value), and update_in(request.options[key], fun) is allowed.

  • Fix typespecs for some functions

  • Deprecate output step in favour of into:!(path).

  • Rename follow_redirects step to redirect

  • redirect: Rename :follow_redirects option to :redirect.

  • redirect: Rename :location_trusted option to :redirect_trusted.

  • redirect: Change HTTP request method to GET only on POST requests that result in 301..303.

    Previously we were changing the method to GET for all 3xx except 307 and 308.

  • decompress_body: Remove support for deflate compression (which was broken)

  • decompress_body: Don't crash on unknown codec

  • decompress_body: Fix handling HEAD requests

  • decompress_body: Re-calculate content-length header after decompresion

  • decompress_body: Remove content-encoding header after decompression

  • decode_body: Do not decode response with content-encoding header

  • run_finch: Add :inet6 option

  • retry: Support retry: :safe_transient which retries HTTP 408/429/500/502/503/504 or exceptions with reason field set to :timeout/:econnrefused.

    :safe_transient is the new default retry mode. (Previously we retried on 408/429/5xx and any exception.)

  • retry: Support retry: :transient which is the same as :safe_transient except it retries on all HTTP methods

  • retry: Use retry-after header value on HTTP 503 Service Unavailable. Previously only HTTP 429 Too Many Requests was using this header value.

  • retry: Support retry: &fun/2. The function receives request, response_or_exception and returns either:

    • true - retry with the default delay

    • {:delay, milliseconds} - retry with the given delay

    • false/nil - don't retry

  • retry: Deprecate retry: :safe in favour of retry: :safe_transient

  • retry: Deprecate retry: :never in favour of retry: false

  • Req.request/2: Improve error message on invalid arguments

  • Req.update/2: Do not duplicate headers

  • Req.update/2: Merge :params

  • Req.Request: Fix displaying redacted basic authentication

  • Req.Request: Add Req.Request.get_option/3

  • Req.Request: Add Req.Request.fetch_option/2

  • Req.Request: Add Req.Request.fetch_option!/2

  • Req.Request: Add Req.Request.delete_option/2

  • Req.Response: Add Req.Response.delete_header/2

  • Req.Response: Add Req.Response.update_private/4

v0.3.11 (2023-07-24)

  • Support Req.get(options),, etc
  • Add
  • retry: Fix returning correct private.req_retry_count

v0.3.10 (2023-06-20)

v0.3.9 (2023-06-08)

v0.3.8 (2023-05-22)

  • Add :redact_auth option to redact auth credentials, defaults to true.
  • Soft-deprecate,run! in favour of Req.Request.run_request/1.

v0.3.7 (2023-05-18)

  • Deprecate setting headers to %NaiveDateTime{}, always use %DateTime{}.
  • decode_body: Add :decode_json option
  • [follow_redirects]: Add :redirect_log_level
  • [follow_redirects]: Preserve HTTP method on 307/308 redirects
  • run_finch: Allow :finch_request to perform the underlying request. This deprecates passing 1-arity function f(finch_request) in favour of 4-arity f(request, finch_request, finch_name, finch_options).

v0.3.6 (2023-03-06)

  • run_finch: Fix setting :hostname option
  • decode_body: Add :extract option to automatically extract archives (zip, tar, etc)

v0.3.5 (2023-02-01)

v0.3.4 (2023-01-03)

  • retry: Add :retry_log_level option

v0.3.3 (2022-12-08)

  • [follow_redirects]: Inherit scheme from previous location
  • run_finch: Fix setting connect timeout
  • run_finch: Add :finch_request option

v0.3.2 (2022-11-14)

  • decode_body: Decode JSON when response is json-api mime type
  • put_params: Fix bug when params have been duplicated when retrying requeset
  • retry: Remove retry: :always option
  • retry: Soft-deprecate retry: :never in favour of retry: false
  • run_finch: Add :transport_opts, :proxy_headers, :proxy, and :client_settings options
  • Req.Response.json/2: Do not override content-type

v0.3.1 (2022-09-09)

  • encode_body: Set Accept header in JSON requests
  • put_base_url: Fix merging with leading and/or trailing slashes
  • Fix merging :adapter option
  • Add get/2, post/2, put/2, patch/2, delete/2 and head/2

v0.3.0 (2022-06-21)

Req v0.3.0 brings redesigned API, new steps, and improvements to existing steps.


The new API allows building a request struct with all the built-in steps. It can be then piped to functions like Req.get!/2:

iex> req = "")

iex> req |> Req.get!(url: "/repos/sneako/finch") |> then(& &1.body["description"])
"Elixir HTTP client, focused on performance"

iex> req |> Req.get(url: "/repos/elixir-mint/mint") |> then(& &1.body["description"])
"Functional HTTP client for Elixir with support for HTTP/1 and HTTP/2."

Setting body and encoding it to form/JSON is now done through :body/:form/:json options:

iex>!("", body: "hello!").body["data"]

iex> req = "")
iex>!(req, form: [x: 1]).body["form"]
%{"x" => "1"}
iex>!(req, json: %{x: 2}).body["form"]
%{"x" => 2}

Improved Error Handling

Req now validates option names ensuring users didn't accidentally mistyped them. If they did, it will try to give a helpful error message. Here are some examples:

Req.request!(urll: "")
** (ArgumentError) unknown option :urll. Did you mean :url? "")
** (ArgumentError) unknown option :bas_url. Did you mean :base_url?

Req also has a new option to handle HTTP errors (4xx/5xx). By default it will continue to return the error responses:

#=> %Req.Response{status: 404, ...}

but users can now pass http_errors: :raise to raise an exception instead:

Req.get!("", http_errors: :raise)
** (RuntimeError) The requested URL returned error: 404
Response body: ""

This is especially useful in one-off scripts where we only really care about the "happy path" but would still like to get a good error message when something unexpected happened.


From the very beginning, Req could be extended with custom steps. To make using such custom steps by others even easier, they can be packaged up into plugins.

Here are some examples:

And here's how they can be used:

  {:req, "~> 0.3.0"},
  {:req_easyhtml, github: "wojtekmach/req_easyhtml"},
  {:req_s3, github: "wojtekmach/req_s3"},
  {:req_hex, github: "wojtekmach/req_hex"},
  {:req_github_oauth, github: "wojtekmach/req_github_oauth"}

req =
  ( :raise)
  |> ReqEasyHTML.attach()
  |> ReqS3.attach()
  |> ReqHex.attach()
  |> ReqGitHubOAuth.attach())

Req.get!(req, url: "").body[".entry-summary h5"]
# #EasyHTML[<h5>
#    Elixir is a dynamic, functional language for building scalable and maintainable applications.
#  </h5>]

Req.get!(req, url: "s3://ossci-datasets").body
# [
#   "mnist/",
#   "mnist/t10k-images-idx3-ubyte.gz",
#   "mnist/t10k-labels-idx1-ubyte.gz",
#   "mnist/train-images-idx3-ubyte.gz",
#   "mnist/train-labels-idx1-ubyte.gz"
# ]

Req.get!(req, url: "").body["metadata.config"]["links"]
#=> %{"GitHub" => ""}

Req.get!(req, url: "").body["login"]
# Outputs:
# paste this user code:
#   6C44-30A8
# at:
# open browser window? [Yn]
# 15:22:28.350 [info] response: authorization_pending
# 15:22:33.519 [info] response: authorization_pending
# 15:22:38.678 [info] response: authorization_pending
#=> "wojtekmach"

Req.get!(req, url: "").body["login"]
#=> "wojtekmach"

Notice all plugins can be attached to the same request struct which makes it really easy to explore different endpoints.

See "Writing Plugins" section in Req.Request module documentation for more information.

Plug Integration

Req can now be used to easily test plugs using the :plug option:

defmodule Echo do
  def call(conn, _) do
    "/" <> path = conn.request_path
    Plug.Conn.send_resp(conn, 200, path)

test "echo" do
  assert Req.get!("http:///hello", plug: Echo).body == "hello"

you can define plugs as functions too:

test "echo" do
  echo = fn conn ->
    "/" <> path = conn.request_path
    Plug.Conn.send_resp(conn, 200, path)

  assert Req.get!("http:///hello", plug: echo).body == "hello"

which is particularly useful to create HTTP service mocks with tools like Bypass.

Request Adapters

While Req always used Finch as the underlying HTTP client, it was designed from the day one to easily swap it out. This is now even easier with an :adapter option.

Here is a mock adapter that always returns a successful response:

adapter = fn request ->
  response = %Req.Response{status: 200, body: "it works!"}
  {request, response}

Req.request!(url: "http://example", adapter: adapter).body
#=> "it works!"

Here is another one that uses the json/2 function to conveniently return a JSON response:

adapter = fn request ->
  response = Req.Response.json(%{hello: 42})
  {request, response}

resp = Req.request!(url: "http://example", adapter: adapter)
#=> [{"content-type", "application/json"}]
#=> %{"hello" => 42}

And here is a naive Hackney-based adapter and how we can use it:

hackney = fn request ->
  case :hackney.request(
       ) do
    {:ok, status, headers, body} ->
      headers = for {name, value} <- headers, do: {String.downcase(name), value}
      response = %Req.Response{status: status, headers: headers, body: body}
      {request, response}

    {:error, reason} ->
      {request, RuntimeError.exception(inspect(reason))}

Req.get!("", adapter: hackney).body["description"]
#=> "Elixir is a dynamic, functional language designed for building scalable and maintainable applications"

See "Adapter" section in Req.Request module documentation for more information.

Major changes

Step changes

  • New step: put_plug

  • New step: put_user_agent (replaces part of removed put_default_headers)

  • New step: compressed (replaces part of removed put_default_headers)

  • New step: compress_body

  • New step: [output]

  • New step: handle_http_errors

  • put_base_url: Ignore base URL if given URL contains scheme

  • run_finch: Add :connect_options which dynamically starts (or re-uses already started) Finch pool with the given connection options.

  • run_finch: Replace :finch_options with :receive_timeout and :pool_timeout options

  • encode_body: Add :form and :json options (previously used as {:form, data} and {:json, data})

  • cache: Include request method in cache key

  • decompress_body, compressed: Support Brotli

  • decompress_body, compressed: Support Zstandard

  • decode_body: Support decode_body: false option to disable automatic body decoding

  • [follow_redirects]: Change method to GET on 301..303 redirects

  • [follow_redirects]: Don't send auth headers on redirect to different scheme/host/port unless location_trusted: true is set

  • retry: The Retry-After response header on HTTP 429 responses is now respected

  • retry: The :retry option can now be set to :safe (default) to only retry GET/HEAD requests on HTTP 408/429/5xx responses or exceptions, :always to always retry, :never to never retry, and fun - a 1-arity function that accepts either a Req.Response or an exception struct and returns boolean whether to retry

  • retry: The :retry_delay option now accepts a function that takes a retry count (starting at 0) and returns the delay. Defaults to a simple exponential backoff: 1s, 2s, 4s, 8s, ...


  • Deprecate calling!(url, body) in favour of!(url, body: body). Also, deprecate!(url, {:form, data}) in favour of!(url, form: data). and!(url, {:json, data}) in favour of!(url, json: data). Same for Req.put!/2.

  • Deprecate setting retry: [delay: delay, max_retries: max_retries] in favour of retry_delay: delay, max_retries: max_retries.

  • Deprecate setting cache: [dir: dir] in favour of cache_dir: dir.

  • Deprecate in favour of manually building the struct.

v0.2.2 (2022-04-04)

  • Relax Finch version requirement

v0.2.1 (2021-11-24)

  • Add :private field to Response
  • Update Finch to 0.9.1

v0.2.0 (2021-11-08)

  • Rename normalize_headers to encode_headers
  • Rename prepend_default_steps to put_default_steps
  • Rename encode and decode to encode_body and decode_body
  • Rename netrc to load_netrc
  • Rename finch step to run_finch
  • Rename if_modified_since to put_if_modified_since
  • Rename range to put_range
  • Rename params to put_params
  • Rename request.uri to request.url
  • Change response/error step contract from f(req, resp_err) to f({req, resp_err})
  • Support mime 2.x
  • Add Req.Response struct
  • Add put!/3 and delete!/2
  • Add run_steps/2
  • Initial support for UNIX domain sockets
  • Accept {module, args} and module as steps
  • Ensure get_private and put_private have atom keys
  • put_default_steps: Use MFArgs instead of captures for the default steps
  • put_if_modified_since: Fix generating internet time
  • encode_headers: Encode header values
  • retry: Rename :max_attempts to :max_retries

v0.1.1 (2021-07-16)

  • Fix append_request_steps/2 and prepend_request_steps/2 (they did the opposite)
  • Add finch/1

v0.1.0 (2021-07-15)

  • Initial release